Laser Eye Surgery System

ABSTRACT

A laser eye surgery system includes a laser source, a ranging subsystem, an integrated optical subsystem, and a patient interface assembly. The laser source produces a treatment beam that includes a plurality of laser pulses. The ranging subsystem produces a source beam used to locate one or more structures of an eye. The ranging subsystem includes an optical coherence tomography (OCT) pickoff assembly that includes a first optical wedge and a second optical wedge separated from the first optical wedge. The OCT pickoff assembly is configured to divide an OCT source beam into a sample beam and a reference beam. The integrated optical subsystem is used to scan the treatment beam and the sample beam. The patient interface assembly couples the eye with the integrated optical subsystem so as to constrain the eye relative to the integrated optical subsystem.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/069,042, filed Oct. 31, 2013, which claims thebenefit of priority to U.S. Provisional Application No. 61/722,048,filed Nov. 2, 2012, the entire contents of which are hereby incorporatedby reference in their entirety for all purposes as if fully set forthherein.

BACKGROUND

Cataract extraction is one of the most commonly performed surgicalprocedures in the world. A cataract is formed by opacification of thecrystalline lens or its envelope—the lens capsule—of the eye. Thecataract obstructs passage of light through the lens. A cataract canvary in degree from slight to complete opacity. Early in the developmentof an age-related cataract the power of the lens may be increased,causing near-sightedness (myopia). Gradual yellowing and opacificationof the lens may reduce the perception of blue colors as thosewavelengths are absorbed and scattered within the crystalline lens.Cataract formation typically progresses slowly resulting in progressivevision loss. Cataracts are potentially blinding if untreated.

A common cataract treatment involves replacing the opaque crystallinelens with an artificial intraocular lens (IOL). Presently, an estimated15 million cataract surgeries per year are performed worldwide. Thecataract treatment market is composed of various segments includingintraocular lenses for implantation, viscoelastic polymers to facilitatesurgical procedures, and disposable instrumentation including ultrasonicphacoemulsification tips, tubing, various knives, and forceps.

Presently, cataract surgery is typically performed using a techniquetermed phacoemulsification in which an ultrasonic tip with associatedirrigation and aspiration ports is used to sculpt the relatively hardnucleus of the lens to facilitate removal through an opening made in theanterior lens capsule. The nucleus of the lens is contained within anouter membrane of the lens that is referred to as the lens capsule.Access to the lens nucleus can be provided by performing an anteriorcapsulotomy in which a small (often round) hole is formed in theanterior side of the lens capsule. Access to the lens nucleus can alsobe provided by performing a manual continuous curvilinear capsulorhexis(CCC) procedure. After removal of the lens nucleus, a synthetic foldableintraocular lens (IOL) can be inserted into the remaining lens capsuleof the eye. Typically, the IOL is held in place by the edges of theanterior capsule and the capsular bag. The IOL may also be held by theposterior capsule, either alone or in unison with the anterior capsule.This latter configuration is known in the field as a “Bag-in-Lens”implant.

One of the most technically challenging and critical steps in thecataract extraction procedure is providing access to the lens nucleus.The manual continuous curvilinear capsulorhexis (CCC) procedure evolvedfrom an earlier technique termed can-opener capsulotomy in which a sharpneedle was used to perforate the anterior lens capsule in a circularfashion followed by the removal of a circular fragment of lens capsuletypically in the range of 5-8 mm in diameter. The smaller thecapsulotomy, the more difficult it is to produce manually. Thecapsulotomy provides access for the next step of nuclear sculpting byphacoemulsification. Due to a variety of complications associated withthe initial can-opener technique, attempts were made by leading expertsin the field to develop a better technique for removal of the circularfragment of the anterior lens capsule prior to the emulsification step.

The desired outcome of the manual continuous curvilinear capsulorhexisis to provide a smooth continuous circular opening through which notonly the phacoemulsification of the nucleus can be performed safely andeasily, but also to provide for easy insertion of the intraocular lens.The resulting opening in the anterior lens capsule provides access fortool insertion during removal of the nucleus and for IOL insertion, apermanent aperture for transmission of the image to the retina of thepatient, and also support of the IOL inside the remaining lens capsulethat limits the potential for dislocation. The resulting reliance on theshape, symmetry, uniformity, and strength of the remaining lens capsuleto contain, constrain, position, and maintain the IOL in the patient'seye limits the placement accuracy of the IOL, both initially and overtime. Subsequently, a patient's refractive outcome and resultant visualacuity are less deterministic and intrinsically sub-optimal due to theIOL placement uncertainty. This is especially true for astigmatismcorrecting (“toric”) and accommodating (“presbyopic”) IOLs.

Problems may also develop related to inability of the surgeon toadequately visualize the lens capsule due to lack of red reflex, tograsp the lens capsule with sufficient security, and to tear a smoothcircular opening in the lens capsule of the appropriate size and in thecorrect location without creating radial rips and extensions. Alsopresent are technical difficulties related to maintenance of the depthof the anterior chamber depth after opening the lens capsule, smallpupils, or the absence of a red reflex due to the lens opacity. Some ofthe problems with visualization can be minimized through the use of dyessuch as methylene blue or indocyanine green. Additional complicationsmay also arise in patients with weak zonules (typically older patients)and very young children that have very soft and elastic lens capsules,which are very difficult to controllably and reliably rupture and tear.

The implantation of a “Bag-in-Lens” IOL typically uses anterior andposterior openings in the lens capsule of the same size. Manuallycreating matching anterior and posterior capsulotomies for the“Bag-in-Lens” configuration, however, is particularly difficult.

Many cataract patients have astigmatic visual errors. Astigmatism canoccur when the corneal curvature is unequal in all directions. An IOLcan be used to correct for astigmatism but requires precise rotationaland central placement. Additionally, IOLs are not typically used forcorrection beyond 5D of astigmatism. Many patients, however, haveastigmatic visual errors exceeding 5D. Higher correction beyond 5Dtypically requires reshaping the cornea to make it more spherical. Thereare numerous existing approaches for reshaping the cornea, includingCorneaplasty, Astigmatic Keratotomy, Corneal Relaxing Incision (CRI),and Limbal Relaxing Incision (LRI). In Astigmatic Keratotomy, CornealRelaxing Incision (CRI), and Limbal Relaxing Incision (LRI), cornealincisions are made in a well-defined manner and depth to allow thecornea to change shape to become more spherical. Presently, thesecorneal incisions are typically accomplished manually often with limitedprecision.

Thus, improved methods and systems for treating cataracts and/orcreating corneal incisions are needed.

SUMMARY

Improved laser eye surgery systems, and related methods, are provided.The laser eye surgery systems use a laser to form precise incisions inthe cornea, in the lens capsule, and/or in the crystalline lens nucleus.In many embodiments, a laser eye surgery system includes a laser cuttingsubsystem to produce a laser pulse treatment beam to incise tissuewithin the eye, a ranging subsystem to measure the spatial dispositionof external and internal structures of the eye in which incisions can beformed, an alignment subsystem, and shared optics operable to scan thetreatment beam, a ranging subsystem beam, and/or an alignment beamrelative to the laser eye surgery system. The alignment subsystem caninclude a video subsystem that can be used to, for example, provideimages of the eye during docking of the eye to the laser eye surgerysystem. In many embodiments, a liquid interface is used between apatient interface lens and the eye. The use of the liquid interfaceavoids imparting undesirable forces to the patient's eye. The alignmentand ranging subsystems may be used to detect structures involved withthe patient interface.

Thus, in one aspect, a laser eye surgery system is provided. The lasereye surgery system includes a laser source, a ranging subsystem, anintegrated optical subsystem, and a patient interface assembly. Thelaser source is configured to produce a treatment beam that includes aplurality of laser pulses. The ranging subsystem is configured toproduce a source beam used to locate one or more structures of an eye.The ranging subsystem includes an optical coherence tomography (OCT)pickoff assembly that includes a first optical wedge and a secondoptical wedge separated from the first optical wedge. The OCT pickoffassembly is configured to divide the source beam into a sample beam anda reference beam. The integrated optical subsystem is configured toreceive the treatment beam, direct the treatment beam to selectedtreatment locations within the eye so as to incise tissue at theselected treatment locations, receive the sample beam, direct the samplebeam to selected measurement locations within the eye, and transmitreturn portions of the sample beam from the selected measurementlocations back to the ranging subsystem for processing by the rangingsubsystem. The patient interface assembly is configured to couple theeye with the integrated optical subsystem so as to constrain the eyerelative to the integrated optical subsystem and provide coupling oftreatment and ranging light to and within the eye.

Variations of the laser eye surgery system are provided. For example,the patient interface assembly can include a patient interface lenshaving a posterior surface spaced from the eye when the patientinterface assembly couples the eye with the integrated opticalsubsystem. The patient interface assembly can be configured toaccommodate a volume of fluid interfaced with both the patient interfacelens posterior surface and the eye. The patient interface assembly canbe configured to demountably couple with the integrated opticalsubsystem to enable replacement of the patient interface assemblybetween treatments. The patient interface assembly can be, for example,a removable assembly, an interchangeable assembly, and/or anexchangeable assembly. The patient interface lens can have an anteriorsurface disposed between the patient interface lens posterior surfaceand the integrated optical subsystem. The ranging subsystem can be usedto locate the patient interface lens anterior surface and the patientinterface lens posterior surface relative to the ranging subsystem andthe integrated optical subsystem. The integrated optical subsystem canbe controlled in part based on the locations of the patient interfacelens anterior and posterior surfaces so as to at least one of saiddirect the treatment beam to selected treatment locations within the eyeto incise tissue at the selected treatment locations or said direct thesample beam to selected measurement locations within the eye. The OCTranging subsystem is split into a reference and sample beam. Thissplitting may be achieved using two optical wedges. Each of the firstand second optical wedges can have non-parallel anterior and posteriorsurfaces. The source beam can propagate through the first optical wedgeand into the second optical wedge. The second optical wedge posteriorsurface can be partially reflective so as to divide the source beam intothe sample beam and the reference beam. The sample beam can propagateout of the second optical wedge through the posterior surface. Thereflected reference beam can propagate out of the second optical wedgethrough the anterior surface and propagate back through the firstoptical wedge and along a reference optical path. A returning portion ofthe sample beam can be at least one of retro-reflected or scattered andreturned back through the second optical wedge. The sample beamreturning portion can propagate back through the first optical wedge.The reference beam, after traversing a path length, can beretro-reflected and can propagate back into the second optical wedgethrough the anterior surface. A reflected portion of the reference beamcan then be reflected by the second optical wedge posterior surface. Thereference beam reflected portion can propagate out of the second opticalwedge through the anterior surface and propagate through the firstoptical wedge. The first and second optical wedges can have the samewedge angle and be arranged such that the wedge angles are opposing. Thewedge angle of the first and second optical wedges can be in a rangefrom 3 degrees to 10 degrees. The wedge angle of the first and secondoptical wedges can be in a range from 5 degrees to 7 degrees. The firstand second optical wedges can be made from the same material having arefractive index of greater than 1.50 with respect to the wavelength ofthe source beam. The refractive index can be greater than 1.70 withrespect to the wavelength of the source beam. The first optical wedgeanterior and posterior surfaces can have an anti-reflection coating. Thesecond optical wedge anterior surface can have the anti-reflectioncoating. The second optical wedge posterior surface can be uncoated. Theanti-reflection coating can be magnesium fluoride (MgF₂). The sourcebeam can have an angle of incidence on the second optical wedgeposterior surface of less than 25 degrees. The angle of incidence can beless than 15 degrees. The OCT pickoff assembly comprised of the twowedges, for example, can be configured to have low angles of incidenceat all surfaces such that the OCT pickoff assembly is substantiallypolarization insensitive. The first and second optical wedges can beseparated by a distance greater than a detection range of the rangingsubsystem to inhibit etalon effects. The second optical wedge anteriorsurface and the first optical wedge posterior surface can benon-parallel to inhibit etalon effects. The second optical wedgeanterior surface and the first optical wedge posterior surface candeviate from parallel by 0.25 degrees to 3.0 degrees to inhibit etaloneffects. The second optical wedge anterior surface and the first opticalwedge posterior surface can deviate from parallel by 0.50 degrees to 1.5degrees to inhibit etalon effects.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a perspective view showing a laser eye surgery system, inaccordance with many embodiments.

FIG. 2 is a simplified block diagram showing a top level view of theconfiguration of a laser eye surgery system, in accordance with manyembodiments.

FIG. 3 is a simplified block diagram illustrating the configuration ofan optical assembly of a laser eye surgery system, in accordance withmany embodiments.

FIGS. 4A, 4B, and 4C are different views of a simplified diagramillustrating the configuration of an optical assembly of a laser eyesurgery system, in accordance with many embodiments.

FIGS. 5 and 6 are simplified diagrams illustrating an OCTpickoff/combiner assembly, in accordance with many embodiments.

FIG. 7 is a simplified diagram illustrating aspects of beam combiners ofa laser eye surgery system, in accordance with many embodiments.

FIG. 8 is a simplified diagram illustrating aspects of using aZ-telescope to change a depth of focus of a treatment beam within aneye, in accordance with many embodiments.

FIG. 9 diagrammatically illustrates a volume within an eye in whichincisions can be formed by a laser eye surgery system, in accordancewith many embodiments.

DETAILED DESCRIPTION

Methods and systems related to laser eye surgery are disclosed. A laseris used to form precise incisions in the cornea, in the lens capsule,and/or in the crystalline lens nucleus. In many embodiments, a laser eyesurgery system includes a laser cutting subsystem to produce a laserpulse treatment beam to incise tissue within the eye, a rangingsubsystem to measure the spatial disposition of external and internalstructures of the eye in which incisions can be formed, an alignmentsubsystem, and shared optics operable to scan the treatment beam, aranging subsystem beam, and/or an alignment beam relative to the lasereye surgery system. The alignment subsystem can include a videosubsystem that can be used to, for example, provide images of the eyeduring docking of the eye to the laser eye surgery system and alsoprovide images of the eye once the docking process is complete. In manyembodiments, a liquid interface is used between a patient interface lensand the eye. The use of the liquid interface avoids impartingundesirable forces to the patient's eye.

System Configuration

FIG. 1 shows a laser eye surgery system 2, in accordance with manyembodiments, operable to form precise incisions in the cornea, in thelens capsule, and/or in the crystalline lens nucleus. The system 2includes a main unit 4, a patient chair 6, a dual function footswitch 8,and a laser footswitch 10.

The main unit 4 includes many primary subsystems of the system 2. Forexample, externally visible subsystems include a touch-screen controlpanel 12, a patient interface assembly 14, patient interface vacuumconnections 16, a docking control keypad 18, a patient interface radiofrequency identification (RFID) reader 20, external connections 22(e.g., network, video output, footswitch, USB port, door interlock, andAC power), laser emission indicator 24, emergency laser stop button 26,key switch 28, and USB data ports 30.

The patient chair 6 includes a base 32, a patient support bed 34, aheadrest 36, a positioning mechanism, and a patient chair joystickcontrol 38 disposed on the headrest 36. The positioning controlmechanism is coupled between the base 32 and the patient support bed 34and headrest 36. The patient chair 6 is configured to be adjusted andoriented in three axes (x, y, and z) using the patient chair joystickcontrol 38. The headrest 36 and a restrain system (not shown, e.g., arestraint strap engaging the patient's forehead) stabilize the patient'shead during the procedure. The headrest 36 includes an adjustable necksupport to provide patient comfort and to reduce patient head movement.The headrest 36 is configured to be vertically adjustable to enableadjustment of the patient head position to provide patient comfort andto accommodate variation in patient head size.

The patient chair 6 allows for tilt articulation of the patient's legs,torso, and head using manual adjustments. The patient chair 6accommodates a patient load position, a suction ring capture position,and a patient treat position. In the patient load position, the chair 6is rotated out from under the main unit 4 with the patient chair back inan upright position and patient footrest in a lowered position. In thesuction ring capture position, the chair is rotated out from under themain unit 4 with the patient chair back in reclined position and patientfootrest in raised position. In the patient treat position, the chair isrotated under the main unit 4 with the patient chair back in reclinedposition and patient footrest in raised position.

The patient chair 6 is equipped with a “chair enable” feature to protectagainst unintended chair motion. The patient chair joystick 38 can beenabled in either of two ways. First, the patient chair joystick 38incorporates a “chair enable” button located on the top of the joystick.Control of the position of the patient chair 6 via the joystick 38 canbe enabled by continuously pressing the “chair enable” button.Alternately, the left foot switch 40 of the dual function footswitch 8can be continuously depressed to enable positional control of thepatient chair 6 via the joystick 38.

In many embodiments, the patient control joystick 38 is a proportionalcontroller. For example, moving the joystick a small amount can be usedto cause the chair to move slowly. Moving the joystick a large amountcan be used to cause the chair to move faster. Holding the joystick atits maximum travel limit can be used to cause the chair to move at themaximum chair speed. The available chair speed can be reduced as thepatient approaches the patient interface assembly 14.

The emergency stop button 26 can be pushed to stop emission of all laseroutput, release vacuum that couples the patient to the system 2, anddisable the patient chair 6. The stop button 26 is located on the systemfront panel, next to the key switch 28.

The key switch 28 can be used to enable the system 2. When in a standbyposition, the key can be removed and the system is disabled. When in aready position, the key enables power to the system 2.

The dual function footswitch 8 is a dual footswitch assembly thatincludes the left foot switch 40 and a right foot switch 42. The leftfoot switch 40 is the “chair enable” footswitch. The right footswitch 42is a “vacuum ON” footswitch that enables vacuum to secure a liquidoptics interface suction ring to the patient's eye. The laser footswitch10 is a shrouded footswitch that activates the treatment laser whendepressed while the system is enabled.

In many embodiments, the system 2 includes external communicationconnections. For example, the system 2 can include a network connection(e.g., an RJ45 network connection) for connecting the system 2 to anetwork. The network connection can be used to enable network printingof treatment reports, remote access to view system performance logs, andremote access to perform system diagnostics. The system 2 can include avideo output port (e.g., HDMI) that can be used to output video oftreatments performed by the system 2. The output video can be displayedon an external monitor for, for example, viewing by family membersand/or training. The output video can also be recorded for, for example,archival purposes. The system 2 can include one or more data outputports (e.g., USB) to, for example, enable export of treatment reports toa data storage device. The treatments reports stored on the data storagedevice can then be accessed at a later time for any suitable purposesuch as, for example, printing from an external computer in the casewhere the user without access to network based printing.

FIG. 2 shows a simplified block diagram of the system 2 coupled with apatient eye 43. The patient eye 43 comprises a cornea, a lens, and aniris. The iris defines a pupil of the eye 43 that may be used foralignment of eye 43 with system 2. The system 2 includes a cutting lasersubsystem 44, a ranging subsystem 46, an alignment guidance system 48,shared optics 50, a patient interface 52, control electronics 54, acontrol panel/GUI 56, user interface devices 58, and communication paths60. The control electronics 54 is operatively coupled via thecommunication paths 60 with the cutting laser subsystem 44, the rangingsubsystem 46, the alignment guidance subsystem 48, the shared optics 50,the patient interface 52, the control panel/GUI 56, and the userinterface devices 58.

In many embodiments, the cutting laser subsystem 44 incorporatesfemtosecond (FS) laser technology. By using femtosecond lasertechnology, a short duration (e.g., approximately 10⁻¹³ seconds induration) laser pulse (with energy level in the micro joule range) canbe delivered to a tightly focused point to disrupt tissue, therebysubstantially lowering the energy level required as compared to thelevel required for ultrasound fragmentation of the lens nucleus and ascompared to laser pulses having longer durations.

The cutting laser subsystem 44 can produce laser pulses having awavelength suitable to the configuration of the system 2. As anon-limiting example, the system 2 can be configured to use a cuttinglaser subsystem 44 that produces laser pulses having a wavelength from1020 nm to 1050 nm. For example, the cutting laser subsystem 44 can havea diode-pumped solid-state configuration with a 1030 (+/−5) nm centerwavelength.

The cutting laser subsystem 44 can include control and conditioningcomponents. For example, such control components can include componentssuch as a beam attenuator to control the energy of the laser pulse andthe average power of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly to adaptthe beam containing the laser pulses to the characteristics of thesystem 2 and a fixed optical relay to transfer the laser pulses over adistance while accommodating laser pulse beam positional and/ordirectional variability, thereby providing increased tolerance forcomponent variation.

The ranging subsystem 46 is configured to measure the spatialdisposition of eye structures in three dimensions. The measured eyestructures can include the anterior and posterior surfaces of thecornea, the anterior and posterior portions of the lens capsule, theiris, and the limbus. In many embodiments, the ranging subsystem 46utilizes optical coherence tomography (OCT) imaging. As a non-limitingexample, the system 2 can be configured to use an OCT imaging systememploying wavelengths from 780 nm to 970 nm. For example, the rangingsubsystem 46 can include an OCT imaging system that employs a broadspectrum of wavelengths from 810 nm to 850 nm. Such an OCT imagingsystem can employ a reference path length that is adjustable to adjustthe effective depth in the eye of the OCT measurement, thereby allowingthe measurement of system components including features of the patientinterface that lie anterior to the cornea of the eye and structures ofthe eye that range in depth from the anterior surface of the cornea tothe posterior portion of the lens capsule and beyond.

The alignment guidance subsystem 48 can include a laser diode or gaslaser that produces a laser beam used to align optical components of thesystem 2. The alignment guidance subsystem 48 can include LEDs or lasersthat produce a fixation light to assist in aligning and stabilizing thepatient's eye during docking and treatment. The alignment guidancesubsystem 48 can include a laser or LED light source and a detector tomonitor the alignment and stability of the actuators used to positionthe beam in X, Y, and Z. The alignment guidance subsystem 48 can includea video system that can be used to provide imaging of the patient's eyeto facilitate docking of the patient's eye 43 to the patient interface52. The imaging system provided by the video system can also be used todirect via the GUI the location of cuts. The imaging provided by thevideo system can additionally be used during the laser eye surgeryprocedure to monitor the progress of the procedure, to track movementsof the patient's eye 43 during the procedure, and to measure thelocation and size of structures of the eye such as the pupil and/orlimbus.

The shared optics 50 provides a common propagation path that is disposedbetween the patient interface 52 and each of the cutting laser subsystem44, the ranging subsystem 46, and the alignment guidance subsystem 48.In many embodiments, the shared optics 50 includes beam combiners toreceive the emission from the respective subsystem (e.g., the cuttinglaser subsystem 44, and the alignment guidance subsystem 48 ) andredirect the emission along the common propagation path to the patientinterface. In many embodiments, the shared optics 50 includes anobjective lens assembly that focuses each laser pulse into a focalpoint. In many embodiments, the shared optics 50 includes scanningmechanisms operable to scan the respective emission in three dimensions.For example, the shared optics can include an XY-scan mechanism(s) and aZ-scan mechanism. The XY-scan mechanism(s) can be used to scan therespective emission in two dimensions transverse to the propagationdirection of the respective emission. The Z-scan mechanism can be usedto vary the depth of the focal point within the eye 43. In manyembodiments, the scanning mechanisms are disposed between the laserdiode and the objective lens such that the scanning mechanisms are usedto scan the alignment laser beam produced by the laser diode. Incontrast, in many embodiments, the video system is disposed between thescanning mechanisms and the objective lens such that the scanningmechanisms do not affect the image obtained by the video system.

The patient interface 52 is used to restrain the position of thepatient's eye 43 relative to the system 2. In many embodiments, thepatient interface 52 employs a suction ring that is vacuum attached tothe patient's eye 43. The suction ring is then coupled with the patientinterface 52, for example, using vacuum to secure the suction ring tothe patient interface 52. In many embodiments, the patient interface 52includes an optically transmissive structure having a posterior surfacethat is displaced vertically from the anterior surface of the patient'scornea and a region of a suitable liquid (e.g., a sterile bufferedsaline solution (BSS) such as Alcon BSS (Alcon Part Number 351-55005-1)or equivalent) is disposed between and in contact with the posteriorsurface and the patient's cornea and forms part of a transmission pathbetween the shared optics 50 and the patient's eye 43. The opticallytransmissive structure may comprise a lens 96 having one or more curvedsurfaces. Alternatively, the patient interface 22 may comprise anoptically transmissive structure having one or more substantially flatsurfaces such as a parallel plate or wedge. In many embodiments, thepatient interface lens is disposable and can be replaced at any suitableinterval, such as before each eye treatment.

The control electronics 54 controls the operation of and can receiveinput from the cutting laser subsystem 44, the ranging subsystem 46, thealignment guidance subsystem 48, the patient interface 52, the controlpanel/GUI 56, and the user interface devices 58 via the communicationpaths 60. The communication paths 60 can be implemented in any suitableconfiguration, including any suitable shared or dedicated communicationpaths between the control electronics 54 and the respective systemcomponents.

The control electronics 54 can include any suitable components, such asone or more processor, one or more field-programmable gate array (FPGA),and one or more memory storage devices. In many embodiments, the controlelectronics 54 controls the control panel/GUI 56 to provide forpre-procedure planning according to user specified treatment parametersas well as to provide user control over the laser eye surgery procedure.

The control electronics 54 may comprise a processor/controller 55(referred to herein as a processor) that is used to perform calculationsrelated to system operation and provide control signals to the varioussystem elements. A computer readable medium 57 (also referred to as adatabase or a memory) is coupled to the processor 55 in order to storedata used by the processor and other system elements. The processor 55interacts with the other components of the system as described morefully throughout the present specification. In an embodiment, the memory57 can include a look up table that can be utilized to control one ormore components of the laser system as described herein.

The processor 55 can be a general purpose microprocessor configured toexecute instructions and data, such as a Pentium processor manufacturedby the Intel Corporation of Santa Clara, Calif. It can also be anApplication Specific Integrated Circuit (ASIC) that embodies at leastpart of the instructions for performing the method in accordance withthe embodiments of the present disclosure in software, firmware and/orhardware. As an example, such processors include dedicated circuitry,ASICs, combinatorial logic, other programmable processors, combinationsthereof, and the like.

The memory 57 can be local or distributed as appropriate to theparticular application. Memory 57 may include a number of memoriesincluding a main random access memory (RAM) for storage of instructionsand data during program execution and a read only memory (ROM) in whichfixed instructions are stored. Thus, memory 57 provides persistent (non-volatile) storage for program and data files, and may include a harddisk drive, flash memory, a floppy disk drive along with associatedremovable media, a Compact Disk Read Only Memory (CD-ROM) drive, anoptical drive, removable media cartridges, and other like storage media.

The user interface devices 58 can include any suitable user input devicesuitable to provide user input to the control electronics 54. Forexample, the user interface devices 58 can include devices such as, forexample, the dual function footswitch 8, the laser footswitch 10, thedocking control keypad 18, the patient interface radio frequencyidentification (RFID) reader 20, the emergency laser stop button 26, thekey switch 28, and the patient chair joystick control 38.

FIG. 3 is a simplified block diagram illustrating an assembly 62, inaccordance with many embodiments, that can be included in the system 2.The assembly 62 is a non-limiting example of suitable configurations andintegration of the cutting laser subsystem 44, the ranging subsystem 46,the alignment guidance subsystem 48, the shared optics 50, and thepatient interface 52. Other configurations and integration of thecutting laser subsystem 44, the ranging subsystem 46, the alignmentguidance subsystem 48, the shared optics 50, and the patient interface52 may be possible and may be apparent to a person of skill in the art.

The assembly 62 is operable to project and scan optical beams into thepatient's eye 43. The cutting laser subsystem 44 includes an ultrafast(UF) laser 64 (e.g., a femtosecond laser). Using the assembly 62,optical beams can be scanned in the patient's eye 43 in threedimensions: X, Y, Z. For example, short-pulsed laser light generated bythe UF laser 64 can be focused into eye tissue to produce dielectricbreakdown to cause photodisruption around the focal point (the focalzone), thereby rupturing the tissue in the vicinity of the photo-inducedplasma. In the assembly 62, the wavelength of the laser light can varybetween 800 nm to 1200 nm and the pulse width of the laser light canvary from 10 fs to 10000 fs. The pulse repetition frequency can alsovary from 10 kHz to 500 kHz. Safety limits with regard to unintendeddamage to non-targeted tissue bound the upper limit with regard torepetition rate and pulse energy. Threshold energy, time to complete theprocedure, and stability can bound the lower limit for pulse energy andrepetition rate. The peak power of the focused spot in the eye 43 andspecifically within the crystalline lens and the lens capsule of the eyeis sufficient to produce optical breakdown and initiate aplasma-mediated ablation process. Near-infrared wavelengths for thelaser light are preferred because linear optical absorption andscattering in biological tissue is reduced for near-infraredwavelengths. As an example, the laser 64 can be a repetitively pulsed1031 nm device that produces pulses with less than 600 fs duration at arepetition rate of 120 kHz (+/−5%) and individual pulse energy in the 1to 20 micro joule range.

The cutting laser subsystem 44 is controlled by the control electronics54 and the user, via the control panel/GUI 56 and the user interfacedevices 58, to create a laser pulse beam 66. The control panel/GUI 56 isused to set system operating parameters, process user input, displaygathered information such as images of ocular structures, and displayrepresentations of incisions to be formed in the patient's eye 43.

The generated laser pulse beam 66 proceeds through a zoom assembly 68.The laser pulse beam 66 may vary from unit to unit, particularly whenthe UF laser 64 may be obtained from different laser manufacturers. Forexample, the beam diameter of the laser pulse beam 66 may vary from unitto unit (e.g., by +/−20%). The beam may also vary with regard to beamquality, beam divergence, beam spatial circularity, and astigmatism. Inmany embodiments, the zoom assembly 68 is adjustable such that the laserpulse beam 66 exiting the zoom assembly 68 has consistent beam diameterand divergence unit to unit.

After exiting the zoom assembly 68, the laser pulse beam 66 proceedsthrough an attenuator 70. The attenuator 70 is used to adjust thetransmission of the laser beam and thereby the energy level of the laserpulses in the laser pulse beam 66. The attenuator 70 is controlled viathe control electronics 54.

After exiting the attenuator 70, the laser pulse beam 66 proceedsthrough an aperture 72. The aperture 72 sets the outer useful diameterof the laser pulse beam 66. In turn the zoom determines the size of thebeam at the aperture location and therefore the amount of light that istransmitted. The amount of transmitted light is bounded both high andlow. The upper is bounded by the requirement to achieve the highestnumerical aperture achievable in the eye. High NA promotes low thresholdenergies and greater safety margin for untargeted tissue. The lower isbound by the requirement for high optical throughput. Too muchtransmission loss in the system shortens the lifetime of the system asthe laser output and system degrades over time. Additionally,consistency in the transmission through this aperture promotes stabilityin determining optimum settings (and sharing of) for each procedure.Typically to achieve optimal performance the transmission through thisaperture as set to be between 88% to 92%.

After exiting the aperture 72, the laser pulse beam 66 proceeds throughtwo output pickoffs 74. Each output pickoff 74 can include a partiallyreflecting mirror to divert a portion of each laser pulse to arespective output monitor 76. Two output pickoffs 74 (e.g., a primaryand a secondary) and respective primary and secondary output monitors 76are used to provide redundancy in case of malfunction of the primaryoutput monitor 76.

After exiting the output pickoffs 74, the laser pulse beam 66 proceedsthrough a system-controlled shutter 78. The system-controlled shutter 78ensures on/off control of the laser pulse beam 66 for procedural andsafety reasons. The two output pickoffs precede the shutter allowing formonitoring of the beam power, energy, and repetition rate as apre-requisite for opening the shutter.

After exiting the system-controlled shutter 78, the optical beamproceeds through an optics relay telescope 80. The optics relaytelescope 80 propagates the laser pulse beam 66 over a distance whileaccommodating positional and/or directional variability of the laserpulse beam 66, thereby providing increased tolerance for componentvariation. As an example, the optical relay can be a keplerian afocaltelescope that relays an image of the aperture position to a conjugateposition near to the XY galvo mirror positions. In this way, theposition of the beam at the XY galvo location is invariant to changes inthe beams angle at the aperture position. Similarly the shutter does nothave to precede the relay and may follow after or be included within therelay.

After exiting the optics relay telescope 80, the laser pulse beam 66 istransmitted to the shared optics 50, which propagates the laser pulsebeam 66 to the patient interface 52. The laser pulse beam 66 is incidentupon a beam combiner 82, which reflects the laser pulse beam 66 whiletransmitting optical beams from the ranging subsystem 46 and thealignment guidance subsystem: AIM 48.

Following the beam combiner 82, the laser pulse beam 66 continuesthrough a Z-telescope 84, which is operable to scan focus position ofthe laser pulse beam 66 in the patient's eye 43 along the Z axis. Forexample, the Z-telescope 84 can include a Galilean telescope with twolens groups (each lens group includes one or more lenses). One of thelens groups moves along the Z axis about the collimation position of theZ-telescope 84. In this way, the focus position of the spot in thepatient's eye 43 moves along the Z axis. In general, there is arelationship between the motion of lens group and the motion of thefocus point. For example, the Z-telescope can have an approximate 2 xbeam expansion ratio and close to a 1:1 relationship of the movement ofthe lens group to the movement of the focus point. The exactrelationship between the motion of the lens and the motion of the focusin the Z axis of the eye coordinate system does not have to be a fixedlinear relationship. The motion can be nonlinear and directed via amodel or a calibration from measurement or a combination of both.Alternatively, the other lens group can be moved along the Z axis toadjust the position of the focus point along the Z axis. The Z-telescope84 functions as a Z-scan device for scanning the focus point of thelaser-pulse beam 66 in the patient's eye 43. The Z-telescope 84 can becontrolled automatically and dynamically by the control electronics 54and selected to be independent or to interplay with the X- and Y-scandevices described next.

After passing through the Z-telescope 84, the laser pulse beam 66 isincident upon an X-scan device 86, which is operable to scan the laserpulse beam 66 in the X direction, which is dominantly transverse to theZ axis and transverse to the direction of propagation of the laser pulsebeam 66. The X-scan device 86 is controlled by the control electronics54, and can include suitable components, such as a motor, galvanometer,or any other well known optic moving device. The relationship of themotion of the beam as a function of the motion of the X actuator doesnot have to be fixed or linear. Modeling or calibrated measurement ofthe relationship or a combination of both can be determined and used todirect the location of the beam.

After being directed by the X-scan device 86, the laser pulse beam 66 isincident upon a Y-scan device 88, which is operable to scan the laserpulse beam 66 in the Y direction, which is dominantly transverse to theX and Z axes. The Y-scan device 88 is controlled by the controlelectronics 54, and can include suitable components, such as a motor,galvanometer, or any other well known optic moving device. Therelationship of the motion of the beam as a function of the motion ofthe Y actuator does not have to be fixed or linear. Modeling orcalibrated measurement of the relationship or a combination of both canbe determined and used to direct the location of the beam.Alternatively, the functionality of the X-scan device 86 and the Y-scandevice 88 can be provided by an XY-scan device configured to scan thelaser pulse beam 66 in two dimensions transverse to the Z axis and thepropagation direction of the laser pulse beam 66. The X-scan and Y-scandevices 86, 88 change the resulting direction of the laser pulse beam66, causing lateral displacements of UF focus point located in thepatient's eye 43.

After being directed by the Y-scan device 88, the laser pulse beam 66passes through a beam combiner 90. The beam combiner 90 is configured totransmit the laser pulse beam 66 while reflecting optical beams to andfrom a video subsystem 92 of the alignment guidance subsystem 48.

After passing through the beam combiner 90, the laser pulse beam 66passes through an objective lens assembly 94. The objective lensassembly 94 can include one or more lenses. In many embodiments, theobjective lens assembly 94 includes multiple lenses. The complexity ofthe objective lens assembly 94 may be driven by the scan field size, thefocused spot size, the degree of telecentricity, the available workingdistance on both the proximal and distal sides of objective lensassembly 94, as well as the amount of aberration control.

After passing through the objective lens assembly 94, the laser pulsebeam 66 passes through the patient interface 52. As described above, inmany embodiments, the patient interface 52 includes a patient interfacelens 96 having a posterior surface that is displaced vertically from theanterior surface of the patient's cornea and a region of a suitableliquid (e.g., a sterile buffered saline solution (BSS) such as Alcon BSS(Alcon Part Number 351-55005-1) or equivalent) is disposed between andin contact with the posterior surface of the patient interface lens 96and the patient's cornea and forms part of an optical transmission pathbetween the shared optics 50 and the patient's eye 43.

The shared optics 50 under the control of the control electronics 54 canautomatically generate aiming, ranging, and treatment scan patterns.Such patterns can be comprised of a single spot of light, multiple spotsof light, a continuous pattern of light, multiple continuous patterns oflight, and/or any combination of these. In addition, the aiming pattern(using the aim beam 108 described below) need not be identical to thetreatment pattern (using the laser pulse beam 66 ), but can optionallybe used to designate the boundaries of the treatment pattern to provideverification that the laser pulse beam 66 will be delivered only withinthe desired target area for patient safety. This can be done, forexample, by having the aiming pattern provide an outline of the intendedtreatment pattern. This way the spatial extent of the treatment patterncan be made known to the user, if not the exact locations of theindividual spots themselves, and the scanning thus optimized for speed,efficiency, and/or accuracy. The aiming pattern can also be made to beperceived as blinking in order to further enhance its visibility to theuser. Likewise, the ranging beam 102 need not be identical to thetreatment beam or pattern. The ranging beam needs only to be sufficientenough to identify targeted surfaces. These surfaces can include thecornea and the anterior and posterior surfaces of the lens and may beconsidered spheres with a single radius of curvature. Also the opticsshared by the alignment guidance: video subsystem does not have to beidentical to those shared by the treatment beam. The positioning andcharacter of the laser pulse beam 66 and/or the scan pattern the laserpulse beam 66 forms on the eye 43 may be further controlled by use of aninput device such as a joystick, or any other appropriate user inputdevice (e.g., control panel/GUI 56) to position the patient and/or theoptical system.

The control electronics 54 can be configured to target the targetedstructures in the eye 43 and ensure that the laser pulse beam 66 will befocused where appropriate and not unintentionally damage non-targetedtissue. Imaging modalities and techniques described herein, such asthose mentioned above, or ultrasound may be used to determine thelocation and measure the thickness of the lens and lens capsule toprovide greater precision to the laser focusing methods, including 2Dand 3D patterning. Laser focusing may also be accomplished by using oneor more methods including direct observation of an aiming beam, or otherknown ophthalmic or medical imaging modalities, such as those mentionedabove, and/or combinations thereof. Additionally the ranging subsystemsuch as an OCT can be used to detect features or aspects involved withthe patient interface. Features can include fiducials placed on thedocking structures and optical structures of the disposable lens such asthe location of the anterior and posterior surfaces.

In the embodiment of FIG. 3, the ranging subsystem 46 includes an OCTimaging device. Additionally or alternatively, imaging modalities otherthan OCT imaging can be used. An OCT scan of the eye can be used tomeasure the spatial disposition (e.g., three dimensional coordinatessuch as X, Y, and Z of points on boundaries) of structures of interestin the patient's eye 43. Such structure of interest can include, forexample, the anterior surface of the cornea, the posterior surface ofthe cornea, the anterior portion of the lens capsule, the posteriorportion of the lens capsule, the anterior surface of the crystallinelens, the posterior surface of the crystalline lens, the iris, thepupil, and/or the limbus. The spatial disposition of the structures ofinterest and/or of suitable matching geometric modeling such as surfacesand curves can be generated and/or used by the control electronics 54 toprogram and control the subsequent laser-assisted surgical procedure.The spatial disposition of the structures of interest and/or of suitablematching geometric modeling can also be used to determine a wide varietyof parameters related to the procedure such as, for example, the upperand lower axial limits of the focal planes used for cutting the lenscapsule and segmentation of the lens cortex and nucleus, and thethickness of the lens capsule among others. Additionally the rangingsubsystem such as an OCT can be used to detect features or aspectsinvolved with the patient interface. Features can include fiducialsplaced on the docking structures and optical structures of thedisposable lens such as the location of the anterior and posteriorsurfaces.

The ranging subsystem 46 in FIG. 3 includes an OCT light source anddetection device 98. The OCT light source and detection device 98includes a light source that generates and emits an OCT source beam witha suitable broad spectrum. For example, in many embodiments, the OCTlight source and detection device 98 generates and emits the OCT sourcebeam with a broad spectrum from 810 nm to 850 nm wavelength. Thegenerated and emitted light is coupled to the device 98 by a single modefiber optic connection.

The OCT source beam emitted from the OCT light source and detectiondevice 98 is passed through a pickoff/combiner assembly 100, whichdivides the OCT source beam into a sample beam 102 and a referenceportion 104. A significant portion of the sample beam 102 is transmittedthrough the shared optics 50. A relative small portion of the samplebeam is reflected from the patient interface 52 and/or the patient's eye43 and travels back through the shared optics 50, back through thepickoff/combiner assembly 100 and into the OCT light source anddetection device 98. The reference portion 104 is transmitted along areference path 106 having an adjustable path length. The reference path106 is configured to receive the reference portion 104 from thepickoff/combiner assembly 100, propagate the reference portion 104 overan adjustable path length, and then return the reference portion 106back to the pickoff/combiner assembly 100, which then directs thereturned reference portion 104 back to the OCT light source anddetection device 98. The OCT light source and detection device 98 thendirects the returning small portion of the sample beam 102 and thereturning reference portion 104 into a detection assembly, which employsa time domain detection technique, a frequency detection technique, or asingle point detection technique. For example, a frequency domaintechnique can be used with an OCT wavelength of 830 nm and bandwidth of100 nm.

Once combined with the UF laser pulse beam 66 subsequent to the beamcombiner 82, the OCT sample beam 102 follows a shared path with the UFlaser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the OCT sample beam 102 is generallyindicative of the location of the UF laser pulse beam 66. Similar to theUF laser beam, the OCT sample beam 102 passes through the Z-telescope84, is redirected by the X-scan device 86 and by the Y-scan device 88,passes through the objective lens assembly 94 and the patient interface52, and on into the eye 43. Reflections and scatter off of structureswithin the eye provide return beams that retrace back through thepatient interface 52, back through the shared optics 50, back throughthe pickoff/combiner assembly 100, and back into the OCT light sourceand detection device 98. The returning back reflections of the samplebeam 102 are combined with the returning reference portion 104 anddirected into the detector portion of the OCT light source and detectiondevice 98, which generates OCT signals in response to the combinedreturning beams. The generated OCT signals that are in turn interpretedby the control electronics to determine the spatial disposition of thestructures of interest in the patient's eye 43. The generated OCTsignals can also be interpreted by the control electronics to measurethe position and orientation of the patient interface 52, as well as todetermine whether there is liquid disposed between the posterior surfaceof the patient interface lens 96 and the patient's eye 43.

The OCT light source and detection device 98 works on the principle ofmeasuring differences in optical path length between the reference path106 and the sample path. Therefore, different settings of theZ-telescope 84 to change the focus of the UF laser beam do not impactthe length of the sample path for an axially stationary surface in theeye of patient interface volume because the optical path length does notchange as a function of different settings of the Z-telescope 84. Theranging subsystem 46 has an inherent Z range that is related to thelight source and detection scheme, and in the case of frequency domaindetection the Z range is specifically related to the spectrometer, thewavelength, the bandwidth, and the length of the reference path 106. Inthe case of ranging subsystem 46 used in FIG. 3, the Z range isapproximately 4-5 mm in an aqueous environment. Extending this range toat least 20-25 mm involves the adjustment of the path length of thereference path via a stage ZED 106 within ranging subsystem 46. Passingthe OCT sample beam 102 through the Z-telescope 84, while not impactingthe sample path length, allows for optimization of the OCT signalstrength. This is accomplished by focusing the OCT sample beam 102 ontothe targeted structure. The focused beam both increases the returnreflected or scattered signal that can be transmitted through the singlemode fiber and increases the spatial resolution due to the reducedextent of the focused beam. The changing of the focus of the sample OCTbeam can be accomplished independently of changing the path length ofthe reference path 106.

Because of the fundamental differences in how the sample beam 102 (e.g.,810 nm to 850 nm wavelengths) and the UF laser pulse beam 66 (e.g., 1020nm to 1050 nm wavelengths) propagate through the shared optics 50 andthe patient interface 52 due to influences such as immersion index,refraction, and aberration, both chromatic and monochromatic, care mustbe taken in analyzing the OCT signal with respect to the UF laser pulsebeam 66 focal location. A calibration or registration procedure as afunction of X, Y, and Z can be conducted in order to match the OCTsignal information to the UF laser pulse beam focus location and also tothe relative to absolute dimensional quantities.

There are many suitable possibilities for the configuration of the OCTinterferometer. For example, alternative suitable configurations includetime and frequency domain approaches, single and dual beam methods,swept source, etc, are described in U.S. Pat. Nos. 5,748,898; 5,748,352;5,459,570; 6,111,645; and 6,053,613.

The system 2 can be set to locate the anterior and posterior surfaces ofthe lens capsule and cornea and ensure that the UF laser pulse beam 66will be focused on the lens capsule and cornea at all points of thedesired opening. Imaging modalities and techniques described herein,such as for example, Optical Coherence Tomography (OCT), and such asPurkinje imaging, Scheimpflug imaging, confocal or nonlinear opticalmicroscopy, fluorescence imaging, ultrasound, structured light, stereoimaging, or other known ophthalmic or medical imaging modalities and/orcombinations thereof may be used to determine the shape, geometry,perimeter, boundaries, and/or 3-dimensional location of the lens andlens capsule and cornea to provide greater precision to the laserfocusing methods, including 2D and 3D patterning. Laser focusing mayalso be accomplished using one or more methods including directobservation of an aiming beam, or other known ophthalmic or medicalimaging modalities and combinations thereof, such as but not limited tothose defined above.

Optical imaging of the cornea, anterior chamber, and lens can beperformed using the same laser and/or the same scanner used to producethe patterns for cutting. Optical imaging can be used to provideinformation about the axial location and shape (and even thickness) ofthe anterior and posterior lens capsule, the boundaries of the cataractnucleus, as well as the depth of the anterior chamber and features ofthe cornea. This information may then be loaded into the laser 3-Dscanning system or used to generate a three dimensionalmodel/representation/image of the cornea, anterior chamber, and lens ofthe eye, and used to define the cutting patterns used in the surgicalprocedure.

Observation of an aim beam can also be used to assist in positioning thefocus point of the UF laser pulse beam 66. Additionally, an aim beamvisible to the unaided eye in lieu of the infrared OCT sample beam 102and the UF laser pulse beam 66 can be helpful with alignment providedthe aim beam accurately represents the infrared beam parameters. Thealignment guidance subsystem 48 is included in the assembly 62 shown inFIG. 3. An aim beam 108 is generated by an aim beam light source 110,such as a laser diode in the 630-650 nm range.

Once the aim beam light source 110 generates the aim beam 108, the aimbeam 108 is transmitted along an aim path 112 to the shared optics 50,where it is redirected by a beam combiner 114. After being redirected bythe beam combiner 114, the aim beam 108 follows a shared path with theUF laser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the aim beam 108 is indicative of thelocation of the UF laser pulse beam 66. The aim beam 108 passes throughthe Z-telescope 84, is redirected by the X-scan device 86 and by theY-scan device 88, passes through the beam combiner 90, passes throughthe objective lens assembly 94 and the patient interface 52, and on intothe patient's eye 43.

The video subsystem 92 is operable to obtain images of the patientinterface and the patient's eye. The video subsystem 92 includes acamera 116, an illumination light source 118, and a beam combiner 120.The video subsystem 92 gathers images that can be used by the controlelectronics 54 for providing pattern centering about or within apredefined structure. The illumination light source 118 can be generallybroadband and incoherent. For example, the light source 118 can includemultiple LEDs. The wavelength of the illumination light source 118 ispreferably in the range of 700 nm to 750 nm, but can be anything that isaccommodated by the beam combiner 90, which combines the light from theillumination light source 118 with the beam path for the UF laser pulsebeam 66, the OCT sample beam 102, and the aim beam 108 (beam combiner 90reflects the video wavelengths while transmitting the OCT and UFwavelengths). The beam combiner 90 may partially transmit the aim beam108 wavelength so that the aim beam 108 can be visible to the camera116. An optional polarization element can be disposed in front of theillumination light source 118 and used to optimize signal. The optionalpolarization element can be, for example, a linear polarizer, a quarterwave plate, a half-wave plate or any combination. An additional optionalanalyzer can be placed in front of the camera. The polarizer analyzercombination can be crossed linear polarizers thereby eliminatingspecular reflections from unwanted surfaces such as the objective lenssurfaces while allowing passage of scattered light from targetedsurfaces such as the intended structures of the eye. The illuminationmay also be in a dark-field configuration such that the illuminationsources are directed to the independent surfaces outside the capturenumerical aperture of the image portion of the video system.Alternatively the illumination may also be in a bright fieldconfiguration. In both the dark and bright field configurations, theillumination light source maybe be used as a fixation beam for thepatient. The illumination may also be used to illuminate the patient'spupil to enhance the pupil iris boundary to facilitate iris detectionand eye tracking. A false color image generated by the near infraredwavelength or a bandwidth thereof may be acceptable.

The illumination light from the illumination light source 118 istransmitted through the beam combiner 120 to the beam combiner 90. Fromthe beam combiner 90, the illumination light is directed towards thepatient's eye 43 through the objective lens assembly 94 and through thepatient interface 94. The illumination light reflected and scattered offof various structures of the eye 43 and patient interface travel backthrough the patient interface 94, back through the objective lensassembly 94, and back to the beam combiner 90. At the beam combiner 90,the returning light is directed back to the beam combiner 120 where thereturning light is redirected toward the camera 116. The beam combinercan be a cube, plate, or pellicle element. It may also be in the form ofa spider mirror whereby the illumination transmits past the outer extentof the mirror while the image path reflects off the inner reflectingsurface of the mirror. Alternatively, the beam combiner could be in theform of a scraper mirror where the illumination is transmitted through ahole while the image path reflects off of the mirrors reflecting surfacethat lies outside the hole. The camera 116 can be an suitable imagingdevice, for example but not limited to, any silicon based detector arrayof the appropriately sized format. A video lens forms an image onto thecamera's detector array while optical elements provide polarizationcontrol and wavelength filtering respectively. An aperture or irisprovides control of imaging NA and therefore depth of focus and depth offield and resolution. A small aperture provides the advantage of largedepth of field that aids in the patient docking procedure.Alternatively, the illumination and camera paths can be switched.Furthermore, the aim light source 110 can be made to emit infrared lightthat would not be directly visible, but could be captured and displayedusing the video subsystem 92.

In the embodiment of FIGS. 4A, 4B, and 4C, the cutting laser subsystem44 includes the ultrafast (UF) laser 64, the zoom assembly 68, thepolarizer and beam dump 70, the output pickoffs 74, the output monitors76, the system-controlled shutter 78, and the optics relay telescope 80.The cutting laser subsystem 44 further includes mirrors 122, 124, 126,128, 130, a periscope 132, a one-half wave plate 134, and an aperture136. The mirrors 122, 124, 126, 128, 130 are used to route the laserpulse beam 66 (treatment beam) from the ultrafast (UF) laser 64 to thebeam combiner 82. The periscope 132 provides an adjustable means toalign the laser pulse beam 66 output by the ultrafast (UF) laser 64 withthe downstream optical path through the downstream portion of thecutting laser subsystem 44, the shared optics 50, the patient interface52, and into the eye 43. The aperture 136 sets an outer useful diameterfor the laser pulse beam 66.

The laser pulse beam 66 passes through the zoom assembly 68. The zoomassembly can be operable to modify beam parameters such as beamdiameter, divergence, circularity, and astigmatism. For example, thezoom assembly 68 illustrated in FIG. 4B is adjustable and includes athree optical element assembly that is adjustable to achieve intendedbeam size and collimation. Although not illustrated here, an anamorphicor other optical system can be used to achieve desired beam parameters.The factors used to determine suitable beam parameters include theoutput beam parameters of the laser, the overall magnification of thesystem, and the desired numerical aperture (NA) at the treatmentlocation. In addition, the zoom assembly 68 can be used to image a laserwaist location or other preferred plane within the laser assembly 64 tothe aperture 136 location, shown in FIG. 4A, for example. The apertureis then imaged by relay 80 to a center location between the X-scandevice 86 and the Y-scan device 88, shown in FIG. 4C. In this way, thebeam at the desired location in the laser such as a waist of stablelocation is placed at the aperture and the portion of the laser pulsebeam 66 that makes it through the aperture 136 is assured to make itthrough the shared optics 50.

After exiting the zoom assembly 68, the laser pulse beam 66 is reflectedby the mirror 124 and the mirror 126 and then passes through theone-half wave plate 134 before passing through the polarizer 70. Thebeam exiting the laser is linearly polarized. The ½ wave plate canrotate this polarization. The amount of light passing through thepolarizer depends on the angle of the rotation of the linearpolarization. Therefore the ½w plate with the polarizer acts as anattenuator of the beam that is transmitted through towards the sharedoptics. The rejected light from this attenuation method is directed intothe beam dump. After exiting the one-half wave plate 134 and polarizer70 combination, the laser pulse beam 66 passes through the aperture 136,through the output pickoffs 74, and through the optics relay telescope80 and the system-controlled shutter 78. By locating thesystem-controlled shutter 78 downstream of the output pickoffs andmonitors 74, 76, the power of the laser pulse beam 66 can be checkedbefore opening the system-controlled shutter 78. After exiting theoptics relay telescope 80, the laser pulse beam 66 is reflected by themirror 128 and the mirror 130. The mirrors 122, 124, 126, 128, 130 inthe cutting laser subsystem 44 can include a coating(s) to controldispersion so as to prevent broadening of the temporal pulse width. Thebeam combiner 82 then reflects the laser pulse beam 66 so as to bedirected through the shared optics 50.

In the embodiment of FIGS. 4A, 4B, and 4C the ranging subsystem 46includes the OCT light source and detection device 98, thepickoff/combiner assembly 100, and the reference path 106. The OCT lightsource and detection device 98 emits the OCT source beam 144, whichpropagates to the pickoff/combiner assembly 100 through a single modeoptical fiber 138 and an optical fiber connector 140. The OCT sourcebeam 144 is collimated using a lens 142 and proceeds towards thepickoff/combiner assembly 100. The function of the pickoff/combinerassembly 100 is to split the OCT source beam 144 into two separate beams(i.e., the sample beam 102 and the reference beam 104). The sample beam102 propagates along an optical path referred to as a sample path. Thereference beam 104 propagates along an optical path referred to as thereference path 106. As described herein, the sample beam 102 propagatesto the eye 43 and is retro reflected or scattered back through thesample path to the pickoff/combiner assembly 100.

The reference beam 104 propagates away from and back to thepickoff/combiner assembly 100 along the reference path 106. Thereference path 106 has an adjustable optical path length to extend themeasurement range within the eye of the ranging subsystem 46. Afterleaving the pickoff/combiner assembly 100, the reference beam 104 isreflected by a mirror 146 so as to pass through an OCT quarter-waveplate 148. After exiting the OCT quarter-wave plate 148, the referencebeam 104 is reflected by a mirror 150 so as to pass lengthwise through aglass rod 152. The material and the length of the glass rod 152 areselected to balance dispersion between the sample path and the referencepath 106. After exiting the glass rod 152, the reference beam 104 passesthrough an aperture 154 and is then reflected by mirrors 156, 158 so asto be directed into a reference path length adjustment mechanism 160,which is repositionable along a direction 162. The mechanism 160includes two mirrors 164 and 166, which are repositioned along thedirection 162 by repositioning the mechanism 160 along the direction162. The reference beam 104 entering the mechanism 160 is reflected bythe mirrors 164, 166. After exiting the mechanism 160, the referencebeam 104 is reflected by a mirror 168 so as to be directed through adispersion element 170, which in combination with the glass rod 152 isselected to balance dispersion between the sample path and the referencepath 106. After exiting the dispersion element 170, the reference beam104 passes through a focusing lens 172 and is reflected by a mirror 174toward a retro mirror 176. The retro mirror 176 retro-reflects thereference beam back along the reference path 106 to the pickoff/combinerassembly 100. The returning sample and reference beams are then combinedby the pickoff/combiner assembly 100. The combined beams with embeddedsignal information is then directed back through the optical fiber 138to the OCT light source and detection device 98 where the combined beamsare detected.

Referring now to FIGS. 5 and 6, the pickoff/combiner assembly 100 isdescribed relative to dividing the OCT source beam 144 into the samplebeam 102 and the reference beam 104. The division of the OCT source beam144 is referred to herein as the pickoff mode. The pickoff/combinerassembly 100 also functions in what is referred to herein as thecombiner mode in which the returning portion of the sample beam 102 andthe returning reference beam 104 are combined and directed back to theOCT light source and detection device 98. The combiner mode workssimilar to the pickoff mode, but in reverse.

The pickoff/combiner assembly 100 includes a first optical wedge 178 anda second optical wedge 180. The OCT source beam 144 passes through thefirst optical wedge 178 and into the second optical wedge 180. The firstoptical wedge 178 has an anterior surface 182 and a posterior surface184. The second optical wedge 180 has an anterior surface 186 and aposterior surface 188. The OCT source beam 144 enters the first opticalwedge 178 through the anterior surface 182 and exits the first opticalwedge 178 through the posterior surface 184. The OCT source beam 144then enters the second optical wedge 180 through the anterior surface186. The OCT source beam 144 is then partially reflected by the secondoptical wedge posterior surface 188. The portion of the OCT source beam144 that is reflected by the posterior surface 188 becomes the referencebeam 104. The portion of the OCT source beam 144 that passes through theposterior surface 188 becomes the sample beam 102. In the embodimentillustrated, each of the first and second optical wedges 178, 180 have awedge angle 190 of 6 degrees. A suitable material for the first andsecond optical wedges 178, 180 can be selected. For example, the firstand second optical wedges can be made from a high refractive index glass(e.g., Schott NSF6 with a refractive index of 1.7826 at wavelength 830nm).

The first and second wedges 178 and 180 are configured to counter-actprism dispersion and color aberration that would result if only oneoptical wedge was used. Passing either the sample beam 102 or thereference beam 104 through a single wedge would result in prismdispersion and color aberration due to the broad bandwidth (e.g., 810 to850 nm) of the OCT source beam 144. The wedge angles of the first andsecond optical wedges 178, 180 are therefore opposing. In this way, eachof the OCT source beam 144, the reference beam 104, and returningportion of the sample beam 102 experiences offsetting wedges effectsbecause the beams pass thru both of the first and second optical wedges178, 180. For example, the reference beam 104 experiences thiscancellation of the wedge effect because the reference beam 104 reflectsoff the second optical wedge posterior surface 188 and then propagatesthrough the second optical wedge 180 and then through the offsettingfirst optical wedge 178.

In many embodiments, the OCT source beam 144 is generally unpolarized.The returning portion of the sample beam 102, however, may have anypolarization including pure s-polarized, pure p-polarized or acombination of both. The polarization of the returning portion of thesample beam 102 is an uncontrolled variable due to polarization effectsimparted by the eye 43. For example, birefringence of the cornea canimpart polarization to the returning portion of the sample beam 102. Thepolarization effects caused by the eye may be dependent on position ofthe sample beam 102 within the eye 43 and subject to anatomicaldifferences. Similar to an interferometer, the OCT light source anddetection device 98 generates an OCT signal based on interferencebetween the returning portion of the sample beam 102 and the referencebeam 104. To achieve signal and contrast, the reference beam 104preferably contains both polarization states. Additionally, thepolarization of the source beam 144 can vary depending on the lightsource used and fiber optic orientation. This can vary from source tosource. The purpose of the ¼w plate in the reference path is to ensurethat a proper amount of both s and p polarization with respect to thesample beam are present in order to generate signal. An extreme exampleis the source beam may be linearly polarized in the p-direction. Thisp-polarized light may be completely converted to s-polarized light dueto uncontrolled anatomical effects upon return in the sample path.Meanwhile in the reference path without a ¼w plate the p-polarization ispreserved. Upon combining the sample and reference paths, the crossedpolarized beams would fail to produce a signal. Introduction of a ¼wplate in the reference beam can convert the p-polarized light intos-polarized reference return light and therefore produce a signal. The¼w plate is adjustable in rotation about its Z axis (clocking).Adjustment can be made on a system to system basis to optimize returnsignal.

In many embodiments, the pickoff/combiner assembly 100 is configured tominimize polarization effects or differences due to beam polarization.For example, as illustrated in Table 1, the illustrated embodiment ofthe pickoff/combiner assembly 100 is configured to minimize the angle ofincidence of the beams (OCT source beam 144, sample beam 102, andreference beam 104) at all of the optical wedge surfaces 182, 184, 186,and in particular at surface 188 so as to minimize polarization effects.

TABLE 1 Example Pickoff/Combiner Assembly Incident Angles and SurfaceCoatings Surface Beam Glass to Air Angle Surface Coating 182 144 12.80degrees Anti-reflection 184 144  2.03 degrees Anti-reflection 186 144 1.03 degrees Anti-reflection 188 144, 102, 104 11.78 degrees Uncoated186 104 22.84 degrees Anti-reflection 184 104 21.84 degreesAnti-reflection 182 104 10.82 degrees Anti-reflection

The offsetting first and second optical wedges 178, 180, the low angleof incidence of the beams 144, 102, 104 relative to the surfaces 182,184, 186, 188, and resulting generation of the OCT signal are importantaspects relative to the configuration of the pickoff/combiner assembly100. For example, a separation 192 between the first and second opticalwedges 178, 180 is preferably greater than the detection range of theOCT light source and detection device 98 for a given length of thereference path 106 so as to reduce and/or eliminate etalon effects fromthe OCT signal. For example, the OCT detection range can be 6.6 mm inair and the separation 192 can be larger than 6.6 mm (e.g., 8 mm orlarger). The etalon effect can be further mitigated by tilting the firstand second wedges 178, 180 relative to each other. For example, in theillustrated embodiment, an angle 194 of the second optical wedgeanterior surface 194 is 89 degrees relative to a normal to the firstoptical wedge posterior surface 184 so that the surfaces 184, 186 aretilted by one degree relative to each other. Although the illustratedembodiment uses a tilt angle of one degree between the surfaces 184,186, any suitable tilt angle can be used.

Because of the low angle of the reference beam 104 relative to the OCTsource beam 144, a certain amount of distance is required before thereference beam 104 is sufficiently separated from the OCT source beam144 to accommodate the mirror 146. For example, a distance 196 (e.g., 43mm) parallel to the OCT source beam 144 and a distance 198 (e.g., 22 mm)perpendicular to the OCT source beam 144 can be used to provide adequateroom for the mirror 146. Because the length of the reference path 106 isadjusted to match the sample path length, distances 200, 202 must beaccounted for in configuring the reference path 106. The separation ofthe first and second optical wedges 178, 180 along with associated wedgeand tilt angles cause an offset 204 between the OCT source beam 144 andthe sample beam 102. The offset 204 must also be accounted for withrespect to positioning optical elements between the pickoff/detectionassembly 100 and the beam combiner 114.

The second optical wedge posterior surface 188 is the beam combiningsurface of the pickoff/detection assembly 100. The surface 188 isuncoated so as to assure reliable reflectivity by eliminating anypossible coating degradation related reflectivity changes. The angle ofincidence at the surface 188 is small to reduce the difference inreflectivity for s and p polarizations. It is important to control theamount of light split between the reference and sample paths. To achievegood signal (as in an interferometer) there is preferably balance in theintensity of the light from both paths. The returning portion of thesample beam 102 is the amount of return generated by reflections andscatter off of a target (e.g., a structure in the eye 43). Generally thereturning portion of the sample beam 102 is relatively low and variable.In contrast, there is little light loss in the reference path 106.Therefore, to maximize light delivered into the eye 43 and to balancethe returning light from both the sample and reference paths, thepickoff/combiner assembly 100 transmits more light than it reflects.Additionally, there is a further safety requirement to limit the amountof light entering the eye 43. Accordingly, as an example, for an OCTsource beam 144 having about 6 mW of light and the above considerations,an 8% reflectivity can be selected as a suitable reflectivity level. The8% reflectivity results in a pickoff percentage of 8% for the referencebeam 104 and 92% for the sample beam 102 or a ratio of 11.5 to 1 sampleto reference. A ratio around 10 to 1 may also be suitable. Thereflectivity for the two polarizations match with respect to each otherto within approximately 10%, [(8.3−7.53)/8.3=9.2%].

Each of the other surfaces 182, 184, 186 has an anti-reflection or ARcoating. The low angle of incidence on these surfaces also assurespolarization insensitivity. Because of the high refractive index of theglass used in the illustrated embodiment, a simple protected magnesiumfluoride MgF₂ coating can be used resulting in a low reflectivity of<0.5% per surface. The simple MgF₂ coating has the advantages ofconsistent control in fabrication and low probability of coatingdegradation.

Using high refractive index glass for the first and second opticalwedges 178, 180 provides advantages over low refractive index glass suchas: high reflectivity (Fresnel reflection) for the uncoated surface atlow angle of incidence, a higher refractive angle for the same angle ofincidence thereby providing separation of the beams, and a simple MgF₂coating provides excellent anti-reflection i.e. lower reflectivity. Adisadvantage of using high refractive index glass for the first andsecond optical wedges 178, 180 is the higher dispersion usuallyassociated with the higher refractive index. The higher dispersion,however, is offset by the offsetting wedge geometry.

Variations in the configuration of the pickoff/detection assembly 100are possible. For example, the pickoff/detection assembly 100 might beconfigured as a single element depending on the bandwidth/wavelengths ofthe OCT source beam 144 and other relevant mechanical considerations.The single element may be a plate beam splitter, a wedged plate, a cube,or other known beam splitting element. The wedge angle 190 of the secondoptical wedge 180 can be different from the wedge angle 190 of the firstoptical wedge 178. The second optical wedge 180 can also be made from adifferent glass from the first optical wedge 178. Beam dumps and baffles(not illustrated) can also be used for unused light reflected from thesurfaces 182, 184, 186, 188.

Referring back to FIGS. 4A, 4B, and 4C, after exiting thepickoff/detection assembly 100, the sample beam 102 is reflected bymirrors 206, 208 and then passes through an aperture 210 before beingincident on the beam combiner 114. The sample beam 102 is transmittedthrough the beam combiner 112 and is then reflected by a mirror 212 soas to be incident on the beam combiner 82. The sample beam 102 istransmitted through the beam combiner 82 into the shared optics 50. Beamaperture 210 may be used to limit the amount of light delivered to theeye. This limit may be set by optical hazard considerations and limits,for example, as set by international standards. The beam aperture 154 inthe reference arm 106 may be used to fine tune the balance of light inthe combined reference and sample arms. The beam aperture 154 can alsoused to limit the amount of light directed into the OCT detector 98 toprevent detector saturation, for example. The aperture 154 may also beused to match reference beam size and numerical aperture to that of thesample.

The mirrors 146, 150, 156, 158, 164, 166, 168, 174, 176, 206, 208 in theranging subsystem 46 can be metal (e.g., silver) coated if possible toreduce and prevent adverse dispersion effects. Alternatively,transmission within the ranging subsystem 46 can be through complexdielectrics where suitable as opposed to reflecting to reduce andprevent adverse dispersion effects.

The alignment guidance subsystem 48 includes the aim beam light source110 and the aim path 112. The aim path 112 transmits the aim beam 108emitted by the aim beam light source 110 to the beam combiner 114. Afterbeing emitted by the aim beam light source 110, the aim beam 108 isreflected by mirrors 214, 216 and then passes through a coupling lens218 into an optical fiber 220. The aim beam 108 emerges from the opticalfiber 220 so as to pass through a collimating lens 222, then through anaperture 224, and then through a beam expander 226. The beam expander226 propagates the aim beam 108 over a distance while accommodatingpositional and/or directional variability of the aim beam 108, therebyproviding increased tolerance for component variation. The beam expander226 relays an image of the aperture 224 to a plane near the galvomirrrors 86 and 88. This plane is an alignment reference plane for thesystem. After the beam expander 226, the aim beam 108 is reflected bymirrors 228, 230, 232 so as to be incident on the beam combiner 114,which reflects the aim beam 108 toward the mirror 212. The aim beam 108is reflected by the mirror 212 so at to be incident on the beam combiner82. The aim beam 108 passes through the beam combiner 82 and continuesinto the shared optics 50.

In many embodiments, the aim beam 108 can be used as a system alignmentaid. By checking/ensuring suitable system alignment on a suitablereoccurring time frame, patient safety may be enhanced. The aim beam 108can also be used as a targeting aid for directing the laser pulse beam66 at target locations in the eye 43. The aim beam 108 can also be usedas a fixation light source to give the patient something to look at tocontrol orientation of the eye 43. The aim beam 108 can also be used formonitoring the angle and position of the X, Y, & Z actuators. This couldbe accomplished by placing a detector or detectors such as positionsensing detectors in the beam or a pickoff of the beam. A pickofflocation may be the reflections off of beam combiner 90. In manyembodiments, the aim beam light source 110 includes a diode laser thatis directly controlled via electrical input with no attenuationrequired.

The shared optics 50 provides a common optical path for the laser pulsebeam 66, the sample beam 102, and the aim beam 108. The shared optics 50includes the beam combiner 114, the beam combiner 82, the Z-telescope84, the X-scan device 86, the Y-scan device 88, the beam combiner 90,and the objective lens assembly 94. The shared optics 50 also includesperiscopes 234, 236, which provide an adjustable means to align thelaser pulse beam 66, the sample beam 102, and the aim beam 108 with thedownstream optical path through the downstream portion of the sharedoptics 50, the patient interface 52, and into the eye 43.

In many embodiments, the shared optics 50 is configured to distributeaberration correction balance amongst the Z-telescope 84, the objectivelens assembly 94, and the patient interface lens 96. Specifically, inmany embodiments, the Z-telescope 84, the objective lens assembly 94,and the patient interface lens 96 are configured such that the totalaberration contribution of all the optical elements in the Z-telescope84, the objective lens assembly 94, and the patient interface lens 96sums to zero as nearly as practicable.

The alignment guidance subsystem 48 further includes the video subsystem92. The video subsystem 92 includes the camera 116, the illuminationlight source 118, and the beam combiner 120.

The video subsystem 92 can be designed for one or more modes ofoperation. For example, the video subsystem 92 can be designed toprovide approach guidance during docking of the eye 43 to the laser eyesurgery system 2. The docking approach guidance mode of operation canutilize dark-field cross-polarized illumination. The docking approachguidance mode of operation can utilize bright field fixation. Once theeye 43 is docked to the laser eye surgery system 2, the video subsystem92 can provide a dark-field cross polarization image of the incisedregion of the eye 43 and the patient interface 52. Once the eye isdocked to the laser eye surgery system 2, the video subsystem 92 canprovide bright-field illumination for automated iris detection.

FIG. 7 illustrates transmission and reflectivity characteristics of thebeam combiner 114 used to combine the aim beam 108 and the OCT samplebeam 102, the beam combiner 82 used to combine the laser pulse beam 66with both the aim beam 108 and the OCT sample beam 102, and the beamcombiner 90 used to reflect an image to the video subsystem 92. The beamcombiner 114 is configured to transmit the OCT sample beam 102 andreflect the aim beam 108. For example, the beam combiner 114 can beconfigured to transmit wavelengths from 780 to 880 nm (both s and ppolarizations) and reflect wavelengths from 635 to 645 nm. The beamcombiner 82 is configured to reflect the laser pulse beam 66 whiletransmitting both the OCT sample beam 102 and the aim beam 108. Forexample, the beam combiner 82 can be configured to reflect wavelengthsfrom 1020 to 1050 nm (including linear polarization) and transmitwavelengths from both 780 to 880 nm and 635 to 645 nm. The beam combiner90 is configured to transmit each of the OCT sample beam 102 and thelaser pulse beam 66, partially reflect the aim beam 108, and reflectillumination light from the illumination light source (e.g., nearinfrared LED illumination—wavelengths from 730 to 740 nm).

FIG. 8 illustrates the use of the Z-telescope 84 to focus the laserpulse beam 66 to different depths within the eye 43. In the illustratedembodiment, the Z-telescope 84 includes a lens 238 and a lens 240. Thedistance (UF ZL) between the lenses 238, 240 determines the depth in theeye 43 at which the laser pulse beam 66 is focused. The distance (UF ZL)determines whether the laser pulse beam 66 is diverging (becoming wider)as the laser pulse beam 66 travels between the lens 240 and the X-scandevice 86, is converging (becoming narrower) as the laser pulse beam 66travels between the lens 240 and the X-scan device 86, or is neitherdiverging or converging (constant width) as the laser pulse beam 66travels between the lens 240 and the X-scan device 86. The more thelaser pulse beam 66 is diverging between the lens 240 and the X-scandevice 86, the deeper the depth in the eye 43 at which the laser pulsebeam 66 is focused. The more the laser pulse beam 66 is convergingbetween the lens 240 and the X-scan device 86, the shallower the depthin the eye 43 at which the laser pulse beam 66 is focused. Table 2provides example values for the distance (UF ZL) between the lenses 238,240, as well as corresponding values of the depth of the focal point (UFZ), corresponding values of the resulting numerical aperture (NA),corresponding values of the diameter of the laser pulse beam 66 at thelens 240, and corresponding values of the diameter of the laser pulsebeam 66 at the X-scan device 86.

TABLE 2 Example Z-telescope settings and corresponding values of focusdepth, numerical aperture, and beam diameters for the laser pulsetreatment beam. Beam Diameter at Beam Diameter at UF ZL UF Z Lens 240X-scan Device 86 (mm) (mm) NA (mm) (mm) 29.314 5.000 0.128 18.61 15.3427.399 8.000 0.137 18.08 16.14 24.950 11.283 0.149 17.40 17.16 24.60011.709 0.150 17.30 17.30 20.564 16.000 0.169 16.18 18.99

In many embodiments, the laser eye surgery system 2 is configured to becapable of delivering laser pulses to tightly focused points to disruptand thereby incise tissue throughout a desired treatment volume withinthe eye 43. For example, FIG. 9 is a diagram illustrating a predictedtreatment volume 242 (hatched area) within which the laser eye surgerysystem 2 is capable of incising tissue. The predicted treatment volume242 is bounded in the transverse directions by an x-direction boundary244 and a y-direction boundary 246. Boundary conditions are determinedby optical model simulation of threshold levels taking into accountnumerical aperture, aberration control, beam quality of the laser,polarization of the laser, pulse width, and optical train transmissionanchored to empirically determined levels of tissue breakdown. To ensurethat there is cutting, the boundaries factor in a margin above thisthreshold. A 2 times or 4 times margin above an empirically determinedthreshold is reasonable given the range of variation that goes intodetermining threshold levels. The predicted treatment volume 242 iswider in the x direction for z values (axial distance from the posteriorsurface of the patient interface lens 96) of less than about 7.25 mm andis wider in the y direction for z values of greater than about 7.25 mm.As shown, the predicted treatment volume 242 encompasses the cornea 248and lens capsule 250 of the eye 43, thereby enabling the creation ofincisions at any desired location in the cornea 248 and lens capsule250.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1-21. (canceled)
 22. An optical coherence tomography (OCT) pickoffassembly for dividing an OCT light source beam into a sample beam and areference beam, comprising: a first optical wedge and a second opticalwedge separated from the first optical wedge, wherein: each of the firstand second optical wedges having non-parallel anterior and posteriorsurfaces; the second optical wedge posterior surface is partiallyreflective so as to divide the source beam into a sample beam and areference beam; the first and second optical wedges have a same wedgeangle and are arranged such that the wedge angles are opposing; andangles of incidence at all surfaces of the first and second opticalwedges are disposed such that the OCT pickoff assembly is substantiallypolarization insensitive.
 23. The system of claim 22, wherein a wedgeangle of the first and second optical wedges is each in a range from 3degrees to 10 degrees.
 24. The system of claim 23, wherein the wedgeangle of the first and second optical wedges is each in a range from 5degrees to 7 degrees.
 25. The system of claim 22, wherein the first andsecond optical wedges are made from the same material having arefractive index of greater than 1.50 with respect to the source beam.26. The system of claim 25, wherein the refractive index is greater than1.70 with respect to the source beam.
 27. The system of claim 22,wherein: the first optical wedge anterior and posterior surfaces have ananti-reflection coating; the second optical wedge anterior surface hasthe anti-reflection coating; and the second optical wedge posteriorsurface is uncoated.
 28. The system of claim 27, wherein theanti-reflection coating is magnesium fluoride (MgF₂).
 29. The system ofclaim 22, wherein the source beam has an angle of incidence on thesecond optical wedge posterior surface of less than 25 degrees.
 30. Thesystem of claim 29, wherein the angle of incidence is less than 15degrees.
 31. The system of claim 22, wherein the second optical wedgeanterior surface and the first optical wedge posterior surface deviatefrom parallel by 0.25 degrees to 3.0 degrees.
 32. The system of claim35, wherein the second optical wedge anterior surface and the firstoptical wedge posterior surface deviate from parallel by 0.50 degrees to1.5 degrees.
 33. An optical coherence tomography (OCT) pickoff assemblyfor dividing an OCT light source beam into a sample beam and a referencebeam, comprising: a first optical wedge and a second optical wedgeseparated from the first optical wedge, wherein: each of the first andsecond optical wedges having non-parallel anterior and posteriorsurfaces; the second optical wedge posterior surface is partiallyreflective so as to divide the source beam into a sample beam and areference beam; the first and second optical wedges have a same wedgeangle and are arranged such that the wedge angles are opposing; and thesecond optical wedge posterior surface is uncoated and the secondoptical wedge anterior surface and the first optical wedge posteriorsurface are non-parallel, so as to inhibit etalon effects.
 34. Thesystem of claim 33, wherein a wedge angle of the first and secondoptical wedges is each in a range from 3 degrees to 10 degrees.
 35. Thesystem of claim 34, wherein the wedge angle of the first and secondoptical wedges is each in a range from 5 degrees to 7 degrees.
 36. Thesystem of claim 33, wherein the first and second optical wedges are madefrom the same material having a refractive index of greater than 1.50with respect to the source beam.
 37. The system of claim 36, wherein therefractive index is greater than 1.70 with respect to the source beam.38. The system of claim 33, wherein: the first optical wedge anteriorand posterior surfaces have an anti-reflection coating; the secondoptical wedge anterior surface has the anti-reflection coating; and thesecond optical wedge posterior surface is uncoated.
 39. The system ofclaim 38, wherein the anti-reflection coating is magnesium fluoride(MgF₂).
 40. The system of claim 33, wherein the source beam has an angleof incidence on the second optical wedge posterior surface of less than25 degrees.
 41. The system of claim 40, wherein the angle of incidenceis less than 15 degrees.
 42. The system of claim 33, wherein the secondoptical wedge anterior surface and the first optical wedge posteriorsurface deviate from parallel by 0.25 degrees to 3.0 degrees.
 43. Thesystem of claim 33, wherein the second optical wedge anterior surfaceand the first optical wedge posterior surface deviate from parallel by0.50 degrees to 1.5 degrees.